Pumping systems are used in many application and in many industries to move fluids from one location to another. Often it is necessary to add one or more special fluids to a base fluid which is being pumped. For example, in fire-fighting equipment it is often necessary and desirable to add a fire retardant chemical to a water stream which is being used to subdue a fire. There are many types of fire retardant chemicals used for this purpose. Typically they create a fire retardant foam when mixed with water and forced through a discharge nozzle.
Typically, conventional pumping equipment used for adding a fire-retardant chemical to the water involves the use of three individual valves. One valve controls water flow, another valve controls chemical addition, and yet another valve controls flushing of the chemical supply line. The use of this plurality of valves leaves much room for operator error. Also, it requires separate operation of the valves at the necessary times in order to obtain the desired addition of chemical to the water. This may not be convenient, particularly where time is of the essence. Further, after the chemical has been added to the water it is necessary to operate the valves in such a manner that the chemical supply line can be properly flushed. Operation of valves also results in changes in the water pressure at the discharge nozzle. This is undesirable.
There has not heretofore been provided a simple and efficient pumping system for adding a controlled amount of a fluid to another fluid while maintaining constant nozzle pressure as described herein.